1. Field of the Invention
The present invention relates to a die device for applying a coating of fluent material to a strand, such as a length of wire, and more particularly to an applicating-die device formed in part of polycrystalline synthetic diamond material.
2. Description of the Prior Art
Strand material, such as wire, is conventionally coated with fluent materials in the form of adhesives or insulators, it being a primary objective to obtain a coating which is of uniform thickness and consistency. In the prior art, apparatus has been used which sprays material on moving conductors, rollers to apply a coating from a bath to a conductor which is advanced thereover at a tangent point of engagement, and dies having orifices have been used, the wire being coated with the fluent material prior to passing to the die, to wipe off excess material and to ensure a uniform coating. Typical of the die-type applicators are those found in U.S. Pat. Nos. 1,551,751; 4,046,103 and 4,281,671. In all three of these patents, the bore is formed in a natural, unsplit diamond suitably mounted in a holder. Since the bore portions of the dies are unsplit, the wire to be coated has to be threaded therethrough, and if a wire has already been thread through a machine, in order to insert the wire into the die, it is necessary to cut it so that it can be inserted. With reference to those die devices having other than flat exit surfaces, coating material collects thereon, eventually hardens and then produces unevenness in the coating as the wire emerges from the die.
Other die devices have been formed from brass in two diametral halves, the two halves being assembled into a cylindrical body through which a coaxial bore is formed. One portion of the bore is of uniform diameter and the other portion tapered, the body being formed with a curvilinear surface on the exit side of the bore. Such dies have been found to perform satisfactorily, but in production they have a relatively short wear life, such as a week. Making the same die of ceramic from a single piece of material results in longer wear life, a period of about nine to ten weeks production use having been experienced.